Electrophotographic copying paper

ABSTRACT

AN ELECTROPHOTOGRAPHIC COPYING PAPER COMPRISING A SUPPORT PAPER AND A PHOTOCONDUCTIVE LAYER (WHICH IS A LIGHT-SENSITIVE LAYER) COATED ON ONE SURFACE OF SAID SUPPORT AND CONTAINING AN ORGANIC PHOTOCONDUCTIVE MATERIAL, WHEREIN SAID PHOTOCONDUCTIVE LAYER FURTHER CONTAINS A METAL NITRATE, WITH OR WITHOUT AN ORGANIC ACID.

Jan. 5, 1971 NARIO YAMAGUCHI L ELECTROPHOTOGRAPHIC COPYING PAPER CHARGEON SURFACE POTENTIAL VOLT) Filed March 18, 1968 CHARGE LIGHT OFF ON 3 060 TIME (SEC) Aime/14% United States atent O1 fice 3,552,959ELECTROPHOTOGRAPHIC COPYING PAPER Nario Yamaguchi and Kazuo Tubuko,Tokyo, Japan, as-

signors to Kabushiki Kaisha Ricoh, Tokyo, Japan, a

corporation of Japan Filed Mar. 18, 1968, Ser. No. 713,893 Claimspriority, application Japan, Mar. 23, 1967, 42/ 17,650 Int. Cl. G03g5/06 U.S. Cl. 961.6 6 Claims ABSTRACT OF THE DISCLOSURE Anelectrophotographic copying paper comprising a support paper and aphotoconductive layer (which is a light-sensitive layer) coated on onesurface of said support and containing an organic photoconductivematerial, wherein said photoconductive layer further contains a metalnitrate, With or without an organic acid.

BACKGROUND OF THE INVENTION Field of the invention The present inventionis concerned with a novel electrophotographic copying paper having ahighly increased sensitivity to light and having a photoconductive layerwhich is formed with an organic photoconductive material, wherein saidphotoconductive layer further contains a specific assistant sensitizer.

Description of the prior art Some of the conventionalelectrophotographic copying papers have employed organic photoconductivematerials such as poly-N-vinyl carbazole as the photoconductivematerials to be contained in the light-sensitive or the photoconductivelayer of the copying papers. Most of these known organic photoconductivematerials have their spectral sensitivity in the limited range ofultraviolet rays, say, 355 m more or less. For this reason, there hasbeen made a proposal to expand the light-sensitivity of thoseelectrophotographic copying papers which utilize organic photoconductivematerials in the formation of their photoconductive layers through tothe range of the visible rays by including, in the photoconductivelayers, an assistant sensitizer which includes: metal halides such aszinc chloride, stannous chloride, aluminum chloride, ferric chloride andstannic chloride; acids such as acetic acid, monochloro acetic acid,dichloro acetic acid and trichloro acetic acid or their anhydrides;quinones such as benzoquinone; aldehydes; and ketones. These additives,however, often failed to enhance the light-sensitivity of thephotoconductive layers formed. In some cases, these additives evendecreased the sensitivity to light of such photoconductive layers,depending on the type of the sensitizing dyestuffs which were included,together with said additives, in the photoconductive layers. Also, inthe event that zinc chloride or ferric chloride was included in thephotoconductive layer, such a photoconductive layer exhibited adifliculty in the electrostatic charging thereof and required arelatively long period of time till the potential of the layer wassaturated. On the other hand, the inclusion of such an additive asdichloro acetic acid or trichloro acetic acid in the photoconductivelayers often caused a reduction in the resistance of the photoconductivelayers to light-fatigue. Whereas, the inclusion of a metal halide suchas ferric chloride or stannic chloride in the photoconductive layercaused an intensive gelation of the solution for use in formingphotoconductive layers, making the procedure of applying the solutiononto a support such as paper difficult.

Patented Jan. 5, 1971 SUMMARY OF THE INVENTION It is, therefore, theobject of the present invention to provide an electrophotographiccopying material having a photoconductive layer formed on one surfacethereof, said layer containing, in combination with an organicphotoconductive material which is the principal component thereof, anassistant sensitiver which consists of a metal nitrate and which iscapable of markedly improving the sensitivity to light of saidphotoconductive layer, Without adversely affecting the electrostaticproperty of this layer, that is to say, without in any way deterioratingthe charge characteristics of the photoconductive layer or withoutreducing the resistance of the photoconductive layer to light-fatigue(in this latter case, the charge characteristic of the photoconductivelayer is deteriorated also).

The metal nitrates which can be employed in the present invention arecomprised of those metals which are contained in the Group I, Group II,Group III and Group VIII of the periodic table.

The assistant sensitizers which are particularly suitable for theobjects of the present invention are those metal nitrates such asmagnesium nitrate, zinc nitrate, sodium nitrate, potassium nitrate,cuprous nitrate, ferrous nitrate, ferric nitrate, cobalt nitrate, nickelnitrate, aluminum nitrate and manganese nitrate. The present inventioncontemplates the complete elimination of the aforesaid drawbacks andinconveniences which have been encountered in the conventionalelectrophotographic copying papers, by the inclusion-in thephotoconductive layer-of such an assistant sensitizer as enumeratedabove in an amount ranging from 0.1% to 15% by weight of the organicphotoconductive material which is contained in the photoconductivelayer.

The present invention also contemplates the provision of anelectrophotographic copying paper whose photoconductive layer furthercontainsin addition to the aforesaid metal nitrate--an organic acid suchas organic carboxylic acids, organic sulphonic acids, organic phosphoricacids, nitrophenols and acid anhydrides in an amount ranging from 5% to50% by weight of the metal nitrate which is contained in thephotoconductive layer.

The aforesaid organic acid which can be used in the present inventionincludes:

Organic carboxylic acids, such as acetic acid and the substitutionproducts thereof, monochloro-acetic acid, dichloroacetic acid,trichloroacetic acid, phenylacetic acid, and 6-methylcoumarinylaceticacid (4); maleic acid; cinnamic acid, benzoic acid,1-(4-diethylamino-benzoyl)- benzene-Z-carboxylic acid, phthalic acid,and tetrachlorophthalic acid, a,{3-dibromo-fi-formyl-acrylic acid(mucobromic acid), dibromo-maleic acid, Z-bromo-benzoic acid, gallicacid, 3-nitro-2-hydroxy 1 benzoic acid, 2-nitrophenoxyacetic acid,Z-nitro-benzoic acid, 3-nitrobenzoic acid, 4-nitro-benzoic acid,3-nitro-4-ethoxy-benzoic acid, 2-chloro-4-nitro-1benzoic acid, 3nitro-4-methoxy-benzoic acid, 4-nitro-1-methyl-benzoic acid,2-chloro-5-nitrol-benzoic acid, 3-chloro-6-nitro-l-benzoic acid,4-chloro- 3-nitro-1-benzoic acid, 5 chloro-3-nitro-2-hydroxy-benzoicacid, 4-chloro-2-hydroxy-benzoic acid, 2,4-dinitro-lbenzoic acid,2-brom0-5-nitro-benzoic acid, 4-chlorophenylacetic acid,2-chloro-cinnamic acid, 2-cyano-cinnamic acid, 2,4-dichlorobenzoic acid,3,5-dinitro-benzoic acid, 3,5-dinitro-salicylic acid, malonic acid,mucic acid, acetosalicylic acid, benzilic acid, butane-tetra-carboxylicacid, citric acid, cyano-acetic acid, cyclohexane-dicarboxylic acid,cyclohexane-carboxylic acid, 9,10-dichloro-stearic acid, fumaric acid,itaconic acid, levulinic acid (levulic acid), malic acid, succinic acid,B-bromo-propionic acid, u-bromo-stearic acid, citraconic acid,di-bromo-succinic acid, pyrene-2,3,7,8-tetra-carboxylic acid, tartaricacid;

Organic sulphonic acids, such as 4-toluenesulphonic acid, and benzenesulphonic acid, 2,4-dinitro-1-methylbenzene-6-sulphonic acid,2,6-dinitro-l-hydroxy-benzene- 4-sulphonic acid,2-nitro-1-hydroxy-benzene-4-sulphonic acid,-4-nitro-1-hydroxy-benzene-Z-sulphonic acid, 3-nitro-2-methyl-l-hydroxy-benzene 5 sulfonic acid, 6-nitro-4-methyl-1-hydroxy-benzene 2 sulfonic acid,4-chl0ro-lhydroxy-benzene-3-sulfonic acid,2-chloro3-nitro-1-methylbenzene-S-sulfonic acid, 2-chloro 1methylbenzene-4- sulfonic acid;

Organic phosphonic acids, such as 4-chloro-3-nitrobenzene-phosphonicacid;

'Nitrophenols, such as 4-nitrophenol, and picric acid;

Acid anhydrides, for example; acetic anhydride, succinic anhydride,maleic anhydride, phthalic anhydride, tetra chlorophthalic anhydride,and chrysene 2,3-8-9- tetra-carboxylic anhydride, dibromo maleic acidanhydride.

Description will hereunder be directed to one example of the proceduresfor preparing the electrophotographic copying papers of the presentinvention.

An organic photoconductive material is dissolved in a solvent such asmonochloro benzene, dimethyl formamide and methylene chloride in such away that the concentration of the organic photoconductive material inthe solvent is in the range of from 5% to 10% by weight of said solvent.To this solution is added a sensitizing dyestu1Tin the form of, forexample, a methanol solution-- in an amount, in terms of the dyestuff,ranging from 0.1% to 2% by weight of the photoconductive material used.Then, a metal nitrate such as those described above is added-in the formof a methanol solution, for example-to the resulting solution in anamount ranging from 0.1% to by Weight of said photoconductive material.The addition, if desired to do so, of the aforesaid organic acid isperformed at the time when the aforesaid metal nitrate is introducedinto the solution. After thoroughly mixing the resulting solution bystirring, the mixed liquid is applied onto one surface of a supportsuchas a sheet of paper, metal plate, a film made with either a syntheticresin or a naturally occurring resinwhich has been already given anelectroconducting treatment. The coated support paper is then dried at atemperature ranging from 100 C. to 150 C. for a period of time rangingfrom 2 to 5 minutes to regulate the moisture content thereof to a levelranging from 4.0% to 4.5% by weight of the support. Thus, anelectrophotographic copying paper having a highly increased sensitivityto light is obtained. It is needless to say that thiselectrophotographic copying paper is conveniently applicable to thosehigh speed electrophotographic copying apparatuses which have beenrecently developed.

The organic photoconductive materials which can be used in the presentinvention include poly-N-vinyl carbazole,poly-N-dimethyl-amino-acenaphthy1ene, poly-N- vinyl-nitro carbazole,polyvinyl naphthalene, polyvinyl- N-dimethyl-amino carbazole,poly-N-diethyl-amino-acenaphthylene, polyvinyl anthracene and polyvinylnitronaphthalene. The present invention is featured in that thoseorganic photoconductive materials of both the electron donating type andthe electron attracting type can be employed equally. As the sensitizingdyestuffs, substantially all of those basic dyes such as Rhodamine B(C.I. No. 45170), Rhodamine G (C.I. No. 45150) Rhodamine S (C.I. No.45050), Methyl Violet (C.I. No. 42535), Ethyl Violet (C.I. No. 42600),Crystal Violet (C.I. No. 42555), Methylene Blue FZ (C.I. No. 52015),Methylene Blue BI-I (C.I. No. 52015), Victoria Blue B (C.I. No. 44045),Brilliant Green GX (C.I. No. 42040), Malachite Green (C.I. No. 42000),Basic Flavine 8G (C.I. No. 75670), Concentrated Auramine G (C.I. No.41005) and Acridine Orange NS (C.I. No. 46005), are usable. According tothe present invention, an equally satisfactory effect can be expectedfrom the inclusion of those sensitizing dyestuffs, irrespective ofwhether these sensitizing dyestuffs are included independently .or inany desired combination in the photoconductive layers.

While, in the present invention, the presence of a metal nitrate in thephotoconductive layer increases greatly the light-sensitivity of themanufactured copying papers as compared with the light-sensitivity ofthe conventional electrophotographic copying papers, it is to be notedthat the inclusionin combinationof an organic acid and a metal nitratein the photoconductive layers will further enhance the light-sensitivityof the copying papers produced.

As has been described, the present invention provides anelectrophotographic copying paper having a highly increased sensitivityto light, by the inclusion of a metal nitrate in the photoconductivelayer which is prepared by the use of an organic photoconductivematerial. Also, the present invention contemplates a further increasingof the light-sensitivity of the photoconductive layer which is formedwith an organic photoconductive material, by the joint inclusion of ametal nitrate and an organic acid such as formic acid or acetic acid inthe photoconductive layer.

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing shows thecurve which represents the electrostatic characteristics of theelectrophotographic copying paper obtained in the following Example 1.The solid line in the drawing denotes the characteristic curve of theelectrophotographic copying paper of the present invention, while thebroken line represents that of the control copying paper which is usedfor the purpose of the comparison of the electrostatic characteristicsof these two copying papers. More specifically, these two curves bothshow the changes in the potential of the photoconductive layers whichoccurred during the period from the time when the copying papers werecharged on, that is to say, when the photoconductive layers wereimpressed with an electric charge by corona discharge, with thesubsequent charge off or the cessation of the charging and then leavingthe copying papers in darkness for a While, to the time of the exposureof these copying papers to light.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1 5 gr. of poly-N-vinylcarbazole was dissolved in gr. of monochloro benzene. To this solutionwas added 1.4 gr. of Rhodamine B 1% methanol solution) to serve as thesensitizing dyestuff. To the resulting mixed solution was added further1.05 gr. of aluminum nitrate (5% methanol solution), and the resultingmixed liquid was stirred thoroughly. This mixed liquid was applied ontoone surface of an art paper which had been already given anelectroconducting treatment to a thickness of 4a. The coated supportpaper was then dried at C. for 5 minutes to regulate its moisturecontent to 4.0%. The electrostatic characteristic of theelectrophotographic copying paper thus obtained is shown by the solidline in FIG. 1. The velocity of the light decay of the copying paperobtained in this example was noted to be about 10 times greater thanthat which was indicated by the electrostatic characteristic (refer tothe broken line in the drawing) of the control copying paper whosephotoconductive layer which was formed with poly-N-vinyl carbazolecontained a sensitizing dyestutf which consisted of Rhodamine B alone.

Example 2 5 gr. of poly-N-vinyl carbazole was dissolved in 95 gr. ofMethyl Cellosolve. To this solution were added 1.5 gr. (1% methanolsolution) of Aizen Magenta, a product of Hodogaya Chemical Co., Ltd. andalso 1.0 gr. 1% methanol solution) of Methylene Blue FZ and further 1.05gr. (5% methanol solution) of zinc nitrate. The mixture was stirredcompletely. Thus, a mixed liquid was prepared. This liquid was applied,to a thickness of 3,u, onto one surface of a mat tracing paper of 60gr./m. which had been given an electroconducting treatment, and wasdried at 100 C. to regulate its moisture content. The copying paper thusobtained showed a light decay which was noted to be about 12 timesgreater in velocity than that of the control copying paper which wasformed without the inclusion of zinc nitrate. The copying paper obtainedin this example was found to be satisfactory with respect to the chargecharacteristic.

Example 3 5 gr. of poly-N-vinyl-nitro carbazole was dissolved in 95 gr.of dimethyl formamide. To this solution were added 1.0 gr. 1% methanolsolution) of Crystal Violet and also 2.0 gr. (5% methanol solution) ofmagnesium nitrate, and the mixture was stirred thoroughly. Thus, a mixedliquid was prepared. This liquid was applied, to a thickness of 4a, ontoone surface of an acetate film which had been given an electroconductingtreatment, and the coated support was dried to regulate the moisturecontent thereof. The copying paper obtained in this way showed a lightdecay which was noted to be about 8 times greater in velocity ascompared with that of the control copying paper which contained nomagnesium nitrate in the photoconductive layer. The copying paper whichmas obtained in this example according to the present invention gave awell-contrasted copied image.

Example 4 5 gr. of polyvinyl carbazole was dissolved in 95 gr. ofmonochloro benzene. To this solution were added 1.0 gr. (1% methanolsolution) of Rhodamine B and also 1.05 gr. (5% methanol solution) ofaluminum nitrate and 0.5 gr. (5% methanol solution) of acetic acid. Theresulting mixed liquid was stirred at 70 C. for 5 minutes and then wascooled to room temperature. The resulting liquid was applied onto oneface of an art paper to a thickness of 5a, and was dried at 120 C. for 2minutes to regulate the moisture content 0 4.5%. The copying paper husobtained showed a light decay which was noted to be about 15 timesgreater in velocity than that of the control copying paper in which thesensitizing dyestufl contained in tis photoconductive layer consisted ofRhodamine B alone. The copying paper also showed only a negligibleamount of light-fatigue. The copied image obtained from this copyingpaper of the instant example was a well-contrasted one.

Aside from the foregoing one, electrophotographic copying papers wereprepared from each combination of aluminum nitrate and an acid, i.e.benzene sulphonic acid, 4-chloro-3-nitro-benzene-phosphoric acid, picricacid and dibromo maleic acid anhydride, respectively, which were used inplace of the acetic acid contained in the composition of the aforesaidmixed liquid.

It was found that the sensitivity to light of the photoconductive layersof these electrophotographic copying papers was substantially equal tothat of the above-described copying paper obtained from the combinationof aluminum nitrate and acetic acid.

What is claimed is:

1. An electrophotographic copying material comprising a support and aphotoconductive layer formed on one surface of said support, said layerconsisting essentially of an organic photoconductive polymeric materialcontaining therein from 0.1 to 15% by weight, based on the weight ofsaid photoconductive polymeric material, of at least one metal nitrateselected from the group consisting of magnesium nitrate, zinc nitrate,sodium nitrate, potassium nitrate, cuprous nitrate, ferrous nitrate,ferric nitrate, cobalt nitrate, nickel nitrate, aluminum nitrate andmanganese nitrate.

2. An electrophotographic copying material according to claim 1, whereinsaid organic photoconductive polymeric material is at least onesubstance selected from the group consisting of poly-N-vinyl carbazole,poly-N- dimethyl-amino-acenaphthalene, poly-N-vinyl-nitro carbazole,polyvinyl napthalene, polyvinyl-N-dimethyl-amino carbazole,poly-N-diethyl-amino acenaphthalene, polyvinyl anthracene and polyvinylnitronapthalene.

3. An electrophotographic copying material according to claim 1, whereinsaid organic photoconductive polymeric material further contains from0.1 to 2% by weight, based on the weight of said photoconductivepolymeric material, of at least one sensitizing dyestuff selected fromthe group consisting of Rhodamine B (C.I. No. 45170), Rhodamine G (C.I.No. 45150), Rhodamine S (C.I. No. 45050), Methyl Violet (C.I. No.42535), Ethyl Violet (C.I. No. 42600), Crystal Violet (C.I. No. 42555),Methylene Blue FZ (C.I. NO. 52015), Methylene Blue BH (C.I. No. 52015),Victoria Blue B (C.I. No. 44045), Brilliant Green CX (C.I. No. 42040),Malachite Green (C.I. No. 42000), Basic Flavine 8G (C.I. No. 75670),Concentrated Auramine G (C.I. No. 41005 and Acridine Orange NS (C.I. No.46005).

4. An electrophotographic copying material comprising support and aphotoconductive layer formed on one surface of said support, said layerconsisting essentially of an organic photoconductive polymeric materialcontaining therein from 0.1 to 15 by weight, based on the weight of saidphotoconductive polymeric material, of at least one metal nitrateselected from the group consisting of magnesium nitrate, zinc nitrate,sodium nitrate, potassium nitrate, cuprous nitrate, ferrous nitrate,ferric nitrate, cobalt nitrate, nickel nitrate, aluminum nitrate andmanganese nitrate, and from 5 to 50% by weight, based on the weight ofsaid metal nitrate, of at least one organic acid selected from the groupconsisting of organic carboxylic acids, organic sulphonic acids, organicphosphoric acids, nitrophenols and acid anhydrides.

5. An electrophotographic copying material according to claim 4, whereinsaid organic photoconductive polymeric material is at least onesubstance selected from the group consisting of poly-N-vinyl carbazole,poly-N- dimethyl-amino-acenaphthalene, poly-N-vi-nyl-nitro carbazole,polyvinyl naphthalene, polyvinyl-N-dimethylamino carbazole,poly-N-diethyl-amino-acenaphthalene, polyvinyl anthracene and polyvinylnitronaphthalene.

6. An electrophotographic copying material according to claim 4, whereinsaid organic photoconductive polymeric material further contains from0.1 to 2% by weight, based on the weight of said photoconductivepolymeric material, of at least one sensitizing dyestuff selected fromthe group consisting of Rhodamine B (C.I. No. 45170), Rhodamine G (C.I.No. 45150), Rhodamine S (C.I. No. 45050), Methyl Violet (C.I. No.42535), Ethyl Violet (C.I. No. 42600), Crystal Violet (C.I. NO. 42555),Methylene Blue FZ (C.I. No. 52015), Methylene Blue BH (C.I. No. 52015),Victoria Blue (C.I. No. 44045), Brillia-nt Green GX (C.I. No. 42040),Malachite Green (C.I. No. 42000), Basic Flavine 8G (C.I. No. 75670),Concentrated Auramine G (C.I. No. 41005), and Acridine Orange NS (C.I.No. 46005 References Cited UNITED STATES PATENTS 2,776,251 1/ 1957Schwartz 2042 3,152,903 10/1964 Shepard et a1. 96-64 3,169,060 2/1965Hoegl 96-1.6 3,287,121 11/1966 Hoegl 96-1.5

GEORGE F. LESMES, Primary Examiner C. E. VAN HORN, Assistant ExaminerUS. Cl. X.R. 96-1.5; 252-501

